Nigel 
October 20th, 2009
This is how Edison's carbon impregnated filament ended up
By the mid 1870s A number of people had patented ways to make a light bulb. The trouble was that their inventions either burnt out very quickly, or were way to expensive. Edison saw an opportunity, bought up a number of the patents, and set to work. He did a lot of hard thinking, and based on that he did a lot of hard working.
During this process a reporter came to see Edison.
“Mr Edison, you’ve tried many thousand times to make a working light bulb, but every single time you have failed. Why are you wasting your time? Why don’t you move on to something you can succeed at?”
“Young man,” responded Edison, “you don’t understand how the world works. I haven’t failed several thousand times. I have successfully identified thousands of combinations that don’t work. I am now thousands of experiments closer to success.”
No matter how much thinking he did first, the experiments were necessary.
The basic idea for a light bulb: pass electricity through something fairly thin so that it becomes white hot.
That’s the principle, but as with most great ideas there were significant obstacles to making even one item that was good enough for regular use, and further problems making the things in large numbers.
Here are the basic hitches:
- If you make something white hot in normal air it tends to burn. Solution: put it inside a glass bubble filled with some gas like Nitrogen which is not particularly keen to react with other stuff even at white heat. That’s one of the three functions of the glass part of a bulb.
- Heating an ordinary piece of wire till it glows takes a lot of energy. The thinner you make the wire the less electricity is needed. So go for something really thin. Edison called it a filament.
- But filaments are easy to break, especially at high temperatures. The slightest vibration could blow the bulb. Aha, so why not find the right material to glow when a current passes through, and impregnate it into a filament made of something stronger. He identified carbon as probably the best material to glow.
- So what do you make the filament of? How thick should it be? How long? Do curves matter? How do you connect the ends to a power supply? How much carbon do you impregnate the filament with? What voltage works best? What happens when the voltage varies, as it will?
- And looking at things from a different angle: how long does the filament last? How many times can you turn it on and off? How much does it cost per hour to run? What changes are needed to have something you can manufacture in large quantities at an acceptable price? Will the light bulbs cope with being transported long distances from factory to where they will be used?
Get the picture?
Edison didn’t come up with the basic ideas for how to make a decent light bulb. He was the guy who did all the hard work needed to develop the idea and turn it into something that worked. He had an attitude to failure that repeatedly took him through to success.
Here’s how the man himself expressed it:
I would construct a theory and work on its lines until I found it was untenable. Then it would be discarded at once and another theory evolved. This was the only possible way for me to work out the problem. … I speak without exaggeration when I say that I have constructed 3,000 different theories in connection with the electric light, each one of them reasonable and apparently likely to be true. Yet only in two cases did my experiments prove the truth of my theory. (as quoted in “Talks with Edison” by George Parsons Lathrop in Harpers magazine, Vol. 80 (February 1890), p. 425)
Many more statements attributed to Edison are available on Wikiquote here.
If you want to search for more info on the net don’t make my first mistake. There is only one d in Edison.
This article is # 4 in the effective goal-setting series.
If you want more articles like this please click the Thank you button just below.
